The focus of this proposal is to determine the in vivo function of an unconventional myosin, 95F myosin, in the Drosophila nervous system. 95F myosin expression is developmentally regulated throughout the life cycle of the fly such that some tissues, including the nervous system, express comparatively higher levels of protein. Preliminary evidence demonstrates that 95F myosin exhibits strong localization of a particulate nature to nerve cell processes of the central nervous system. Because 95F myosin has been shown to be a motor that transports cytoplasmic particles in the early embryo, the particulate staining in neurons may indicate that 95F myosin is associated with particles and may be responsible for their transport. Therefore, I am proposing to investigate the in vivo function of 95F myosin in developing neurons in culture. I plan to analyze 95F myosin-mediated motility and 95F myosin distribution in vivo with a GFP-95F myosin fusion. I will also examine the effects of mutations in 95F myosin to determine whether 95F myosin is important for neuronal development and/or transport within neurons. Finally, l plan to determine the nature of 95F myosin-containing particles in mature neurons and perform detailed analysis of 95F myosin protein distribution in the embryonic nervous system. The proposed experiments will provide new information about the in vivo functions of 95F myosin, as well as the actin-based transportation mechanisms in neurons.